Let's get to know the three-phase power transformer together.

Three-phase power transformer consists of a core, coils, casing, insulating bushings, oil reservoir, breathing apparatus, explosion-proof tube, radiator, thermometer and oil level gauge. Disconnect switches, cooling systems, protection devices, etc. The core and the coil are the most important parts of A Transformer, and they are collectively referred to as the "body" of the transformer

1.Core: It consists of two parts: the core column and the iron yoke. The coil is mounted on the core column, while the iron yoke is used to complete the entire magnetic circuit. To reduce the magnetic hysteresis and eddy current losses within the iron core, the iron core is usually made of silicon steel sheets with a higher silicon content and a thickness of 0.35 to 0.5 millimeters. The sheets are coated with insulating paint. According to the different configurations of coils and cores, transformers are classified into two types: core-type and shell-type. In a shell-type transformer, the iron core is wrapped outside the coil, while in a core-type transformer, the coil is wrapped outside the iron core. The shell-type transformer has good heat conductivity and high mechanical strength. However, its manufacturing process is complex. Apart from very small Power Transformers, it is rarely used at present. The manufacturing process of core-type transformers is simple and they are widely used.
2.The composition of the coil: The coils of a transformer are wound using insulated copper or aluminum wires. In each transformer, the coil that receives power from the source and absorbs electrical energy is called the primary coil, also known as the primary side coil or the primary winding. The coil at the output end of electrical energy is called the secondary coil, also known as the secondary side or the auxiliary coil. Sometimes, the coil connected to the high-voltage side of the transformer is called the high-voltage coil, while the one connected to the low-voltage side is called the low-voltage coil. Depending on the different arrangements of the primary and secondary coils in the core, the transformer coil structure can be divided into two types: concentric type and overlapping type.
3.Shell: The transformer shell is usually made by welding steel plates. The body of the transformer is placed in the box, and the box is filled with transformer oil. Transformer oil has two functions: insulation and heat dissipation. During operation, the core of the coil will generate eddy currents and magnetic hysteresis losses. The coils of the transformer have a certain DC resistance, which will cause certain power loss. Eventually, all these losses will result in heat. The transformer oil transfers these heat to the box walls. Depending on the capacity of the transformer, heat dissipation pipes are installed on the box walls to disperse the heat into the air.
4.Insulation bushing: The insulation bushing is the component that connects the high and low voltage windings of the power transformer to the external lines. The leads of the high and low voltage coils of the transformer should be led out from the box and connected to the outside. The leads must be insulated from the grounded box, and this can be achieved by using insulating bushings. The bushing not only serves as an insulator for connecting the leads to the ground, but also performs the function of fixing the leads. The bushings of the power transformer must have the specified voltage rating, sufficient mechanical strength and good thermal stability.
5.Oil reservoir: During the operation of the transformer, the oil expands due to heat. When the transformer stops running or the temperature drops, the oil contracts. However, the oil inside the transformer always remains full. At the same time, it also reduces the contact area between the transformer and the air, in order to minimize the impact of oxidation and moisture on the transformer. To observe the oil level in the oil tank, an oil level gauge is installed at one end of the tank, which indicates the oil volume. The oil in the tank must not exceed the maximum and minimum marks.
6.Respirator: There is a respirator on the oil tank. The upper end of the breathing tube protrudes above the oil tank, and the lower end is outside the oil tank and is equipped with a glass container. Inside the container, there is desiccant to absorb the moisture in the air within the oil tank.
7.Explosion-proof tube: It is a trumpet-shaped tube installed at the top of the transformer, with the tube opening sealed by a diaphragm. Its function is that when a short-circuit fault occurs inside the transformer, the transformer oil decomposes into a large amount of gas, causing the pressure in the oil pipe to increase. At this time, the membrane at the opening of the explosion-proof tube is first ruptured, and the oil gas is thus released, reducing the pressure inside the oil tank and preventing the oil tank from exploding or deforming due to a sudden increase in pressure.